Grain Weight Converter
Convert grains between grains, grams, and milligrams.
What it does
Grains weigh powder charges, arrows, and jewels. One grain is exactly 64.79891 milligrams by definition. Grams suit larger masses with the same scale.
The tool above converts among grains, grams, and milligrams. The defaults convert 500 grains, so the page opens showing 32399.455 mg. Pick new units to update the result.
Base in milligrams is value times factor: grains times 64.79891, grams times 1000. Result divides by target factor. Here 500 times 64.79891 is 32399.455 mg, or 32.3995 g.
Use grains for reloading and archery, milligrams for lab small masses, grams for general weighing. Keep grains weight apart from grain count for seeds.
This page shows the factor, one full hand checked example at 500 grains, a reference table, and practice checks that run through the tool.
How to use
- Type the weight number.
- Pick the starting unit.
- Pick the target unit.
- Read the main result.
- Use grains for charges, grams for bulk.
- Do not mix weight grains with seed counts.
Formula
- gr
- Grains weight unit.
- mg
- Milligrams, base here.
- g
- Grams, 1000 mg.
Exact by definition. Doses need calibrated scales regardless of units.
Worked example
Example: 500 grains to mg
A charge totals 500 grains. Express in milligrams.
- Write 500, from gr, to mg.
- Multiply: 500 x 64.79891 = 32399.455 mg.
- Grams mirror: 32.3995 g.
- Check: 32399.455 / 64.79891 = 500 gr back.
- Use a powder scale for charges.
- Log grains with load data.
Reference table
| Grains | Milligrams | Grams |
|---|---|---|
| 1 | 64.7989 mg | 0.0648 g |
| 100 | 6479.891 mg | 6.4799 g |
| 500 | 32399.455 mg | 32.3995 g |
Limits
- Weight grains only. Seed counts differ.
- Four decimals suit loading. Lab micro work may need more.
- No dose advice here.
- Scales must be calibrated.
Common mistakes
- Reading gr as grams.
- Mixing grains with grams in one product.
- Rounding before converting.
- Using seed counts as weight grains.
- Trusting uncalibrated scales for charges.
Try it yourself
Quick checks. Answers sit tucked under each question.
1 g in grains?
1000 / 64.79891 = 15.4324 gr.
500 gr in g?
32399.455 / 1000 = 32.3995 g.
Questions
500 grains in mg?
32399.455 mg.
Grain?
64.79891 mg exact.
Grams?
Divide mg by 1000.
Use?
Powder, arrows, jewels.
Seeds?
Different. Weight grains only here.
Scale?
Calibrated powder scale for charges.